The invention relates to an x-ray diagnostic generator comprising switching means for switching-on and -off the high voltage transformers at predetermined times.
In switching on a high voltage transformer, after approximately half of the time period of the supply waveform (i.e. the duration of a half cycle pulse), a magnetization peak current occurs which can amount to a multiple of the steady state magnetization current. The most unfavorable instance is provided when the switch-on operation is effected when a phase passes through zero. A high switch-on current pulse (or surge), however, due to the inner voltage drop in the x-ray diagnostic generator, leads to a voltage intrusion (penetration) which is undesirable.
The switch-on current surge can be kept low if always the positive or negative voltage maximum, in the case of a three phase generator of one of the three phases, is selected as the fixed switch-on and -off time. However, this has the disadvantage that only switch-on times of integral multiples of the mains period duration can be realized, and the shortest switching time is restricted to the period duration.